A polycarbonate is generally produced using a raw material derived from a petroleum resource. However, due to recent fear of exhaustion of petroleum resources, it is demanded to provide a polycarbonate using a raw material obtained from a biomass resource such as plant. Also, because of concern that global warming resulting from increase or accumulation of carbon dioxide emissions may bring about climate change or the like, it is demanded to develop a polycarbonate using a plant-derived monomer as the raw material and being carbon neutral even after treating a disposal use.
Conventionally, a technique of obtaining a polycarbonate by using isosorbide as a plant-derived monomer and effecting transesterification with diphenyl carbonate has been proposed (see, for example, Patent Document 1). However, the polycarbonate obtained is brown and is not satisfied. As for the copolymer carbonate of isosorbide and other dihydroxy compounds, a polycarbonate obtained by copolymerizing bisphenol A has been proposed (see, for example, Patent Document 2), and an attempt to improve the rigidity of a homopolycarbonate composed of isosorbide by copolymerizing isosorbide and an aliphatic diol has been made (see, for example, Patent Document 3).
On the other hand, as for the polycarbonate obtained by polymerizing 1,4-cyclohexanedimethanol which is an alicyclic dihydroxy compound, a large number of proposals have been made (see, for example, Patent Documents 4 and 5), but these polycarbonates are a low-molecular-weight polycarbonate having a molecular weight of about 4,000 at most and therefore, many products have a low glass transition temperature.
In this way, a large number of polycarbonates using isosorbide have been proposed, nevertheless, a polycarbonate obtained by copolymerizing isosorbide and an alicyclic dihydroxy compound is not reported and optical constants such as refractive index and Abbe number are also not disclosed.
Patent Document 1: GB 1079686
Patent Document 2: JP-A-56-55425
Patent Document 3: WO2004/111106
Patent Document 4: JP-A-6-145336
Patent Document 5: JP-B-63-12896